Electrical signaling



L. COHEN ELECTRICAL S IGNALING 1922 2 Sheets-Sheet 1 Filed Jan. l6

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LOUIS COHEN, OF WASHINGTON, DISTRICT OF COLUMBIA.

ELEGTBICAL SIGNALING.

Application filed January 16, 1922. Serial No. 529,686.

To all whom it may concern: current will leak away to-ground since the 55 Be it known that I, LOUIS Comm, residloop circuit has the equivalent effect of ,a

ing in Washington, District of Columbia, very high resistance for the frequency ot I have invented certain new and useful Imthe signal it is desired to receive. To be provements in Electrical Signaling, of sure a small amount of current leakage to Which the following is a specification. ground will occur due to the capacity of the so This invention relates to the art of radio metal tube to ground, but this will be small signaling and particularly to improvements compared to the capacity current flow to the in receiving radio signals and a system for coil at the point of connection of the metal use i ti i th me, tube. As a result of this, it can be shown The object of the present invention is to theoretically, that the part of the wave coil 65 eliminate interference and electro-static diswhich is enclosed in the metal tube acts turbances in the reception of radio signals, like a lumped inductance shunted by a ca-' and thus improve the clearness and reliabilpacit-y, simply introducing an additional imity of radio communication. pedance in the antenna circuit. By proper- The method involved consists in the use ly adjusting the length of the wave coil 7 of a sectional wave conductor as part of enclosed in the metal tube, the position and the antenna circuit. This sectional wave connection of the metal tube on the wave conductor is preferably made in the form coil, the total impedance of the antenna cirof on or more long helices wound with cuit including the antenna, any intermediate copper i i i l or lti l l y r inductance and capacity, and the part of the 7 parts of the system of wave coils being enwave coil enclosed inthe metal tube, may

closed in metal tubes which are in electrical be reduced to 'a minimum and thereby obconnection at one point with the wave coil. tain a relatively large sign l Current at the The electrical constants of the wave coils, point where themetal tube iS connected to inductance, capacityand resistance, are disthe W ve coil, and from there on the signal 80 tributed in character, but the capacity of current is propagated along the rest of the the sections of the wave coils which are Wave coil in the form of a wave which is enclosed in the metal tubes is difierent from de c ed at a suitable point on the wave th capacity of the sections of the wave coil by the usual detecting instrumentalicoils which are free, and hence the system ties. c5

of wave coils has difi'erent wave propaga- For any other electrical efiects acting on tion "characteristics for the different parts the antenna which may be due to interferand is therefore, the equivalent of a s cing signals or static disturbances, the loop tional wave conductor. Each metal tube is circuit no longer functions as the equivalent also grounded through a loop circuit conof a high resistance, and therefore most 90 sisting of an inductance and capacity in of the capacity current from the wave coil parallel. By adjusting the electrical conto the metal tube finds its way direct to stants, inductance and capacity of the loop ground through the loop circuit, with the circuit, So as to bring it into resonance for result that the interfering electrical effects the frequency of the signal which it is deare'propagated along that part of the wave 5 sired to receive, it has the equivalent eilect coil enclosed in the. metahtube, as well as of a very high resistance in the circuit behe rest of the wave coil, in the form of a tween the metal tube and ground for curwave which is attenuated as it progresses rents of that particular frequency, and as a ng its path. 1 a fi p t f e consequence. the capacity currents from the urr nt flow in the coil will find its way 'unction point where the wave coil to the tube will find'their way to ground at the 3 back into the wave coil at the point of conmetal tube is connected to the coil because nection between the metal tube and the wave of the low resistance loop circuit path. coil, since there is a difierence of potential Further, the two parts of the wave coil, one between the point on the wave coil where of which is enclosed in the metal tube and the connection is made to the metal tube the other which is tree, have different elecand the parts of the wave coil enclosed in tllcal characteristics, particularly the cathe metal tube. Very little of the capacity pacity constants, an therefore the wave undergoes a reflection at the junction of these two sections of the wave coil which serves to still further reduce the intensity of the wave in its progress along the entire wave coil. It is evident that this method offers a means for rendering the reception of radio signals free from interfering effects by rapidly damping out the others by leakage, reflection and attenuation.

It is obvious that by the use of several sections, the alternate parts of which are enclosed in metal tubes and grounded through separate loop circuits, 3. still greater advantage may be gained in the matter of reducing interfering effects on the detect ing instrument. 1

The principle of operation and the method of using this invention can be better understood by reference to the accompanying diagrammatic figures which show typical embodiments of the invention and form part of this specification.

In the accompanying drawings;

Figure 1 is a diagrammatic view of a system for carrying out the invention in which a single metal tube covering one section of the wave coil is used.

Figure 2 is a modification in which two separate metal tubes enclosing difierentparts of the wave coil are employed.

Figure "3 is an arrangement in which a loop antenna, a wave coil and one metal tube is used.

Having more particular reference to the drawings, and in connection with which like characters of reference will designate corresponding parts throughout, in Figure 1, the antenna 1 is connected to a variable condenser 2 and the wave coil 3, 10 all in series: the metal tube 4 is connected to the wave coil at the point 9 and is also grounded at 8 through the connection 5 and loop circuit 7. 6. The metal ring 11 constitutes an electro-static connection to the grid of a threeelectrode vacuum tube detector 14 to the wave coil 10. The circuit 12, 13 together with the regenerative coupling coil 15, is for the purpose of generating oscillations of a different frequency from that of the incoming signals and by combining the effects on the detector beats are produced giving an audible note which is heard in the telephone 16.

The operationis as follows: The loop 6, 7, is adjusted to be in resonance for the frequency of the signals to be received and gives thereby the equivalent effect of a very high resistance in the circuit 5. 6. 7, 8, for that particular frequency, and, as a consequence, the capacity currents from the portion 3 of the wave coil to the metal tube 4 flow towards 9 and then in the coil portion 10 in the form of a wave, since the coil portion 10 has distributed inductance and capacity, the capacity being principally the capacity of the coil to ground. The part of the wave coil portion 3 which is enclosed in the metal tube 4 acts in this case as the equivalent of a lumped inductance shunted by a capacity, the capacity being that between the coil and the metal tube and has therefore, the same effect as that of an impedance in the antenna circuit, which may be a somewhat complicated function of the inductance, capacity and frequency. By properly adjusting the variable capacity 2, length of the end of the coil portion 3 which is not enclosed in the tube, the length of the tube, all in relation to the antenna, the frequency of the signal and the size of the wave coil employed, the total impedance of the antenna circuit up to the junction point .9 may be made a minimum, thereby enhancing the signal effect which from that point on is propagated on the balance of the wave coil portion 10. and detected through the electrostatic connection 1 For any other electrical effects acting on the antenna which may be due either to interfering signals or ele tro-static disturbances, the circuit 5, 6, '7, 8, acts as a low resistance leak to ground, and therefore the part of the wave coil portion 3 which is enclosed in the metal tube 4 no longer acts as the equivalent of a lumped inductance shunted by a capacity as in the'case of the signal frequency, but rather as a distributed inductance and capacity. In this case the capacity current from the wave coil to the metal tube flows direct to ground, since the loop circuit has a small resistance for any frequency differ ng from the frequency for which the circuit is tuned. The undesirable electrical disturbances are propagated on -the wave coil enclosed in the metal tube as well as on the balance of the wave coil extending beyond the metal tube in the form of a wave which is attenuated in its travel along the ent re wave coil. We have, therefore, a condition where foreign disturbances travel in the form of waves over considerably longer conductors and are therefore at tenuated to a much greater extent than the signals desired to be received. Also foreign disturbances traveling along the coil portion 3 have a low resistance path through the loop circuit when it reaches the junction point 9, and therefore a considerable part of that current is shunted away to ground at that point and only part of that current is transmitted to the balance of the wave coil extending beyond the junction point 9. Further for foreign disturbances, we have in this arrangement, the equivalent condition of two conductors of different distributed electrical characteristics, the capacity per unit length of the part of the wave coil which is enclosed in a metal tube being greater than the capacity per unit length of the wave coil which a relatively small wave coil portion 10 extends beyond the metal tube. Also, the inductance per unit length of the two sections of the wave coil may be made diiferent if desired, but in any case, because of the diiference in the electrical characteristics, a reflection of the wave occurs at the junction point thereby further reducing the efi'ects'of the disturbances which are transmitted on the balance of the wave coil portion 10. Due to the combination of all these con tributing factors mentioned above, leakage, reflection, attenuation, very little if any of interfering disturbances can reach the far end of the Wave coil portion 10 to afiect the detector.

Figure 2 is a modification in which two different sections of the wave coil are enclosed in two separate metal tubes 4 and 4: each metal tube being grounded'through a separate loop circuit 5, 6, 7, 8 and 5', 6', 7, 8', respectively, thereby effecting a progressive reduction in foreign disturbances. the statements made above in connection with Figure 1 apply in this case to each of the two separate sections enclosed in the different metal tubes and any, residual effect which may find its way into the coil beyond that part enclosed in the metal tube 4 is still further reduced in its passage along the section of the wave coil which is enclosed in the metal tube 4 thus offering a means for still further reducing interfering efiects in the reception of radio signals. In this figure the detector is directly connected to the at the point 24. embodiment of this invenloop antenna is employed.

23 is tuned to the frebe received, and the 23 is impressed on Figure 3 is an tion in which a The antenna circuit 22, quency of the signals to potential of condenser the wave coil 3, 10 effecting a wave development on it, the principle of operation being the same as that described in connection with the other two figures.

It is obvious that various modifications may be made without departing from the spirit of the invention. The detector connection may be either direct or electro-static in all of the figures, but for purposes of illustration 2. direct connection is shown in one figure. and an electro-static connection in the other two figures. Also the loop circuit may be connected tube as shown in the figures or through an intermediate impedance, preferably a condenser. Also one form of a three electrode detector circuit is shown in all the figures but any circuit may be employed. It is obviously within the province of this invention to introduce these variations.

I claim:

,1. In a system for radio signaling comprising an antenna, wave coil, part of said wave coil being enclosed in an adjustable directlyto the metal 7 other form of detector or detector metal tube, said metal tube being electrically connected to a point on the said wave coil, and also being grounded through a loop circuit, and detecting instruments associated electrically with said wave coil.

2. In a system for radio signaling comprising an antenna, wave coil, a variable condenser, part of said wave coil being enclosed in an adjustable metal tube, said metal tube being connected electrically to a point on the said wave coil, and also being grounded through a loop circuit and detecting instruments associated electrically with said wave coil.

3. In a system of radio signaling comprising an antenna, variable condenser, wave .coil, part of said wave coil being enclosed in an adjustable grounded metal tube, said metal tube being connected electrically to a point on the said wave coil, and also being grounded through a loop circuit, said loop 1 circuit being adjusted to be in resonance for the frequency of the signals to be received, and a detecting instrument associated electrically with the said wave coil.

4. In a system of radio signaling comprising an antenna, variable condenser. wave coil, part of said wave coil bein enclosed in an adjustable grounded meted tube, said metal tube being connected electrically to a point on the said wave coil, and also being grounded through a loop circuit, said loop circuit being adjusted to be in resonance for the frequency of the signals to be received and a detecting instrument associated electro-statically with the said wave coil.

5. A system of radio signaling comprising an antenna, a variable condenser, a wave coil, sections of said wave coil being enclosed in separate metal tubes, said metal tubes being electrically connected at difierent points to the said wave coil, and also being separately grounded through separate loop circuits, and a detecting instrument connected electrically to said wave coil.

6. A. system of radio signaling comprising an antenna, a variable condenser, a wave coil, sections of said wave coil being enclosed in separate metal tubes, said metal tubes being connected electrically at different points to the said wave coil, and also being separately grounded through separate loop circuits, each of said loop circuits being separately tuned to be in resonance for the frequency of the signal desired to be received, and a detecting instrument connected electrically to said wave coil.

7. In a system of radio signaling comprising a loop antenna, variable condenser, wave coil, part of said wave coil being enclosed in an adjustable grounded metal tube, said metal tube being connected electrically to a point on the said wave coil and also being grounded through a loop circuit, said loop circuit being adjusted to be in resonance for the frequency or the signals to be rethe said wave coil and also being separately ceived and a detecting instrument associgrounded through separate loop circuits, ated electrically with the said Wave coil. each of said loop circuits being separately 8. A system of radio signaling compristuned to be in resonance for the frequency 5 ing a loop antenna, a variable condenser, of the signal desired to be received, and

a Wave coil, sections of said Wave coil being detecting instruments connected electrically enclosed in separate metal tubes, said metal to said wave coil. tubes being connected at different points to LOUIS CORN. 

